The background of the invention is emergency situations that have occurred at sea in context of handling big loads from floating vessels, particularly during bad weather conditions. Under such conditions, a big load may become unmanageable, for example displaced, whereby the vessel and its crew are at risk of becoming seriously damaged and/or shipwrecked.
Particularly in context of towing and relocation of mobile installations at sea, it is customary to use so-called anchor handling vessels. Such vessels comprise spooling apparatuses for spooling of chains, fibre lines and/or wires. The purpose of such a vessel may be to tow a floating installation to a particular position and then to anchor the installation to the seabed by means of a suitable mooring system.
Typically, such a mooring system will comprise a line having a lower end connected to a large and heavy anchor, and having an upper end carried back to the installation. The line may also be a compound line and thus comprise portions of length consisting of different types of line of different shape and/or material type, for example a chain, a fibre line and/or a wire. Thereby, the line may also be of a more or less flexible construction.
For placement and pulling of such an anchor, the associated line will be attached to a spooling apparatus, the apparatus of which generally is disposed at the forward end of the deck of the anchor handling vessel. The line extends from the spooling apparatus, further across the deck and down into the water at the aft end of the vessel. During such an anchor handling operation, the total weight of the anchor and the line may amount to several hundred tonnes. Chain links made of steel, which are used in this context, may possibly have a transverse dimension in the order of 5-10 cm and may a weight in the order of 100-200 kg/meter.
During such an anchor handling operation, however, unforeseen incidents may arise causing the vessel to become exposed to unmanageable forces via the line attached to the vessel. For example, it may relate to the line displacing itself over the side of the vessel and causing it to become lop-sided, which at worst may cause the vessel to capsize and possibly sink.
An example of the latter is the vessel Bourbon Dolphin which, during an anchor handling operation offshore Shetland on Apr. 12, 2007, capsized and finally sunk at a depth of ca. 1100 meters. Several of the vessel's crew members perished in context of the capsizing. The vessel was in the process of pulling up a so-called Bruce anchor attached to a chain and wire having a total weight in the order of 200-300 tonnes.
In view of such unfortunate and disastrous incidents associated with load-burdened lines extending from floating vessels, it would therefore be very advantageous if such lines could be severed as fast as possible in a controlled and safe manner for personnel and equipment, for example via remote control. It would also be advantageous if it was possible to cut all types of line potentially being used on a particular vessel, for example a chain, a fibre line and/or a wire. A technical solution which, when in an emergency situation, brings about such severing possibilities would be able to limit adverse effects and possibly prevent disasters causing crew members, the vessel and/or equipment to perish.